The semiconductor industry has experienced exponential growth. Continuous advancements in lithographic resolution have been made to support critical dimensions (CDs) of 90 nm to 65 nm, 45 nm, 32 nm, 22 nm, 16 nm and beyond. New techniques in lithography have been developed, such as immersion lithography, multiple patterning, extreme ultraviolet (EUV) lithography and e-beam lithography. The challenges being raised by new lithography techniques are not only in resolution but also in economy (e.g. cost of upgrading and loss of throughput). Many developments have focused on improving resolution with reduced loss of process throughput. However, current methods have not been satisfactory in all respects.